A survey of 68 top City institutions by the Bank of England found that 54pc of respondents reckoned the probability of a short-term "high-impact event" to be "high or very high" – a level not witnessed since the survey began in July 2008, just two months before Lehmans' tipped the world into recession. Respondents said they feared a eurozone debt crisis and another economic downturn most.

The findings underline the scale of the crisis the UK faces if Europe's leaders can not strike a deal to calm bond markets. Last week, the Bank warned that the UK was on the brink of a second credit crunch as the eurozone crisis has caused funding markets to dry up.

According to the Bank's twice-yearly Systemic Risk Survey, funding risk is also at its highest level on record, with 57pc of respondents citing it as a major concern – a reading only surpassed by sovereign debt risk and a slide back into recession. Last week's Inflation Report revealed that banks' funding in the three months to September had also fallen to levels not seen since Lehmans collapsed.

Research by Fitch, the ratings agency, reinforced the concerns.

It found that US money market funds – a major source of bank finance – have cut their exposure to UK lenders by 25pc since the end of May. Britain's funding squeeze was not as bad as Europe's, which has had 42pc of US money withdrawn, but worse that the Nordic region, which has lost just 15pc.

Mike Amey, a managing director at bond house Pimco, warned separately on Tuesday that UK banks were not yet in a position to withstand a systemic European crisis involving multiple defaults. He added that any outcome to the eurozone crisis "that does not involve multiple defaults is starting to look like a good result."

Some 68pc of respondents to the Bank's survey raised concerns about European sovereign risk, including fears of a break-up of the euro, disorderly debt restructuring, or sovereign default. Another 13pc expressed concerns about a UK "rating downgrade, loss of confidence in fiscal solvency or the gilt market, a debt crisis, and government default".